High current volume H- ion source with multi-aperture extractor

We describe a high current volume H- ion source, which produces more than 1 A H- ion beams. H- ions formed by volume processes in a magnetically filtered multicusp plasma generator have been extracted through a multi-aperture extractor. The extractor consists of four grids, each has 209 apertures of 9 mm diam within a rectangular area of 12 x 26 cm2. The ion beam current was measured calorimetrically and it was confirmed that H- ion beams of up to 1.26 A were extracted with a current density of 9.5 mA/cm2 at 21 keV for 0.2 s. Impurity concentration in the beam was less than a few percent according to momentum mass analysis